Field of the Disclosure
Embodiments of the present invention relate to a display device, and more particularly, to a display device with integrated touch screen.
Discussion of the Related Art
Touch screens are a type of input device that is included in image displaying devices such as Liquid Crystal Displays (LCDs), Field Emission Displays (FEDs), Plasma Display Panel (PDPs), Electroluminescent Displays (ELDs), and Electrophoretic Display (EPDs), and allows a user to input information by pressing or touching a touch sensor of a screen with a finger, a pen or the like while a user looks at the screen of the image displaying device.
Recently, there is an increasing demand for a display device with integrated touch screen of in-cell type in which elements constituting the touch screen are provided inside the display device so as to realize slimness in mobile terminals such as smart phone and tablet PC.
In case of a general in-cell type touch screen, touch data is transmitted to a system once every one vertical sync signal Vsync to define one frame period. Hereinafter, a driving method of a general display device with integrated touch screen of in-cell type will be described with reference to FIG. 1.
FIG. 1 is a timing diagram illustrating signals of display time and touch time during one frame in a general display device with integrated touch screen.
In case of a general display device with integrated self-capacitive touch screen of an in-cell type, as shown in FIG. 1, display time (D) and touch time (T) are time-divisionally driven according to a data enable DE signal during one frame based on one vertical sync signal.
If using both a display pixel and a touch sensor, a capacitance is affected by a touch sensing for a specific gray level of display, whereby display video content is directly shown in a touch.
For example, a gray level of display data generates an initial capacitance value in a panel regardless of touch, and the capacitance value may exceed a capacitance variation in touch input.
FIG. 2 illustrates values of touch data measured with respect to gray level data of a panel in a general display device with integrated touch screen.
As shown in FIG. 2, on the assumption that a panel 100 is divided into four parts, that is, the panel 100 is classified into black screen and white screen, when white level data is outputted to a display screen, an initial capacitance value is within a range of 60˜125 regardless of touch in touch sensing. Especially, although not shown, an entire screen is changed from the black screen to the white screen, the initial capacitance value is increased up to 90˜260.
This initial capacitance value exceeds the range of 0˜120, that is, the change range of touch data value in the touch input, whereby touch sensitivity may be lowered by the initial capacitance value of the panel 100, and ghost noise may generate. In other words, if data which is inputted to the panel 100 at a moment when the screen is changed from display time to touch time is the white level data, a touch sensing accuracy of the panel 100 may be deteriorated.